For the structure of an optical cable bundled by a plurality of coated optical fibers, a variety of structures such as tape-slotted type and loose-tube type are known (see Non-Patent Document 1). A tape-slotted type of optical cable is excellent in contained efficiency of the coated optical fiber; there occurs easily bending in the coated optical fiber during the manufacture or using, which tends to increase micro-bending loss. On the other hand, a loose-tube type of optical cable is characterized in that an increase of the micro-bending loss is small though it is inferior to the contained efficiency of the coated optical fibers as compared to the tape-slotted type of optical cable.    Non-Patent Document 1: Gunther Mahike, et al., “Fiber Optic Cables, Fundamentals Cable Design System Planning”, 4th revised and enlarged edition, 2001, Publics MCD Corporation Publishing